Heart rate monitor



FIG. 1 is an isometric view of a heart rate monitor;

FIG. 2 is another isometric view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is an end view thereof; and,

FIG. 7 is a rear view thereof. 

CLAIM The ornamental design for a heart rate monitor, as shown and described. 